A Tunisian man who allegedly worked as a bodyguard for Osama bin Laden has been deported from Germany, more than a decade after his asylum bid was first rejected, officials have said.

The 42-year-old, identified by German authorities only as Sami A and by Tunisia as Sami Idoudi, had lived in Germany for more than two decades, but outrage over his presence grew in recent months as Berlin cracks down on refused asylum seekers.

"I can confirm that Sami A was sent back to Tunisia this morning and handed over to Tunisian authorities," interior ministry spokeswoman Annegret Korff told reporters on Friday, following a report in the top-selling Bild newspaper.

"He was placed under arrest just after his arrival in Tunis," a spokesman for the Tunisian anti-terrorism force, Sofiene Sliti, told the AFP news agency.

Sami A had previously successfully argued against his deportation, saying he risked being tortured in his homeland.

Never charged

A court in the city of Gelsenkirchen ruled against the deportation late on Thursday, upholding the assessment that the suspect potentially faced "torture and inhumane treatment".

However, the decision only reached federal authorities, by fax, on Friday morning, after Sami A's flight to Tunisia had taken off, the DPA news agency reported.

Considered a security threat over his suspected ties to armed groups, Sami A has for years had to report to police but was never charged with an offence.

He has always denied being the former bodyguard of bin Laden, the mastermind behind the 9/11 attacks on the United States.

Judges in a 2015 case in the German city of Muenster however said they believed Sami A underwent military training at an al-Qaeda camp in Afghanistan in 1999 and 2000 and belonged to bin Laden's team of guards.

German authorities first rejected Sami A's asylum request in 2007 but prosecutors' efforts to expel him were repeatedly blocked by courts citing the danger of torture in Tunisia.

Minister's intervention

An unrelated court ruling last month involving another Tunisian man, accused over a 2015 attack on Tunis' Bardo museum, helped pave the way for Sami A's expulsion.

In that instance, German judges found that the accused did not face the threat of the death penalty as Tunis has had a moratorium on implementing capital punishment since 1991.

Horst Seehofer, Germany's interior minister, seized on the precedent to say he hoped Sami A would be next, calling on migration officers to make the case "a priority".

Bild led a vocal campaign against Sami A's presence in Germany, reporting that he collected nearly 1,200 euros ($1,400) a month in welfare benefits.